1. Field of the Invention
The present invention relates to an ink that is suitable for a mark layer of a golf ball.
2. Description of the Related Art
Golf balls used for playing golf at a golf course are formed with a mark layer for the purpose of denoting a trademark, a numbers for distinguishing the players, the manufacturer and the like. On the other hand, golf balls for use in a golf practice range that is called “driving range” are formed with a mark layer denoting the name of the practice range, and with a linear mark layer for an antitheft purpose. These mark layers are formed from ink.
The mark layer may be directly printed on a body of the ball, alternatively, may be printed on a base coat layer, which is usually a white paint, formed on the surface of a body of the ball. When the mark layer is directly printed on a body of the ball, a crosslinked rubber or an ionomer resin may often be a base for the mark layer. In general, a finishing coat layer, which consists of a clear paint, is formed on the mark layer for the purpose of the protection of the mark layer. This finishing coat layer plays a role in the improvement of the appearance, the prevention of the pollution, and the like.
A golf ball is repeatedly hit with a golf club, and repeatedly impacts on the ground surface. Through the hitting and the impact, the finishing coat layer is gradually worn out or exfoliated. Concomitant with this event, the mark layer also gradually disappears. Upon disappearance of the mark layer, the appearance of the ball is deteriorated, and in addition, the function of the denotation of the mark layer itself is also impaired. A mark layer that insufficiently adheres to its base is liable to disappear. Therefore, inks having excellent adhesiveness to bases are of a great concern to the golf ball manufacturers.
Aiming at the improvement of the adhesiveness, a variety of investigations have been conducted for the modification of inks in both respects of the base materials and the curing agents. Japanese Patent No. 3102817 (U.S. Pat. No. 5,160,536) discloses a golf ball having a mark layer formed from an ink, which comprises nitrocellulose as a base material. Japanese Patent Publication Reference JP-A 122271/1997 (U.S. Pat. No. 5,770,325) discloses a golf ball having a mark layer formed from an ink that contains an ultraviolet curable resin and a photopolymerization initiator. Japanese Patent Publication Reference JP-A 303012/2000 discloses a golf ball having a mark layer formed from an ink that contains acrylpolyol and isocyanate. Japanese Patent Publication Reference JP-A 40260/2001 discloses a golf ball having a mark layer formed from an ink that contains a vinyl resin as a base material, and isocyanate.
However, it is still in a status that a mark layer having sufficient adhesiveness to the base has not been achieved yet. In particular, insufficient adhesion tends to result when no base coat layer is provided, and thus a mark layer is directly printed on the body of the ball. Accordingly, there exist urgent needs for the improvement of inks.